A POS system has a POS terminal located at a checkout counter, and a printer connected to the communication port of the POS terminal. A POS application for printing receipts, and a printer driver that controls driving the printer, run on the POS terminal. The printer driver generates print data that causes the printer to print based on application data generated by the POS application, and controls the printer to print by sending the print data to the printer.
A dedicated driver based on the UnifiedPOS specification is commonly used as the printer driver that operates on the POS terminal. As described in PTL 1, when the first start service request is received from the POS application, this dedicated driver occupies the communication port for the POS application. More specifically, the dedicated driver enables printing only application data from the POS application by the printer. The dedicated driver continues occupying the communication port while the POS application is running. As a result, the POS system prevents the receipt printing process from being interrupted.